[layout] Make build-time filesystem layout explicit

Prior to this change the build-time filesystem layout was created
implicitly from the package names. This method breaks for nested
workspaces where package names differ depending on their context.

This makes built-time layout explicit by introducing a "layout" section
in the package description. If no explicit layout is set, leeway will
fall back to its prior behaviour and use the dependency's filesystem
safe name. This mechanism is implemented during linking s.t. the
build-time layout stays stable across nested workspaces.

`leeway describe` has been updated accordingly to show the layout.
`leeway vet` finds layout path clashes if two dependencies occupy the
same path at build-time.

Author: Christian Weichel

cmd/describe.go

@@ -159,6 +159,7 @@ type packageDescription struct {
 	Manifest     map[string]string            `json:"manifest" yaml:"manifest"`
 	ArgDeps      []string                     `json:"argdeps,omitempty" yaml:"argdeps,omitempty"`
 	Dependencies []packageMetadataDescription `json:"dependencies,omitempty" yaml:"dependencies,omitempty"`
+	Layout       map[string]string            `json:"layout,omitempty" yaml:"layout,omitempty"`
 	Config       configDescription            `json:"config,omitempty" yaml:"config,omitempty"`
 	Env          []string                     `json:"env,omitempty" yaml:"env,omitempty"`
 	Definition   string                       `json:"definition,omitempty"`
@@ -181,11 +182,17 @@ func newPackageDesription(pkg *leeway.Package) packageDescription {
 	}
 	sort.Slice(deps, func(i, j int) bool { return deps[i].FullName < deps[j].FullName })
 
+	layout := make(map[string]string)
+	for _, dep := range pkg.GetDependencies() {
+		layout[dep.FullName()] = pkg.BuildLayoutLocation(dep)
+	}
+
 	return packageDescription{
 		Metadata:     newMetadataDescription(pkg),
 		Type:         string(pkg.Type),
 		ArgDeps:      pkg.ArgumentDependencies,
 		Dependencies: deps,
+		Layout:       layout,
 		Env:          pkg.Environment,
 		Manifest:     manifest,
 		Config:       newConfigDescription(pkg.Type, pkg.Config),
@@ -249,6 +256,10 @@ Version Relevant Arguments:
 Dependencies:
 {{- range $k, $v := .Dependencies }}
 {{"\t"}}{{ $v.FullName -}}{{"\t"}}{{ $v.Version -}}
+{{ end }}
+Layout:
+{{- range $k, $v := .Layout }}
+{{"\t"}}{{ $k -}}{{"\t"}}{{ $v -}}
 {{ end -}}
 {{ end }}
 {{ if .Manifest -}}

pkg/leeway/build.go

@@ -619,7 +619,7 @@ func (p *Package) buildYarn(buildctx *buildContext, wd, result string) (err erro
 			return PkgNotBuiltErr{deppkg}
 		}
 
-		tgt := deppkg.FilesystemSafeName()
+		tgt := p.BuildLayoutLocation(deppkg)
 		if cfg.Packaging == YarnOfflineMirror {
 			fn := fmt.Sprintf("%s.tar.gz", tgt)
 			commands = append(commands, []string{"cp", builtpkg, filepath.Join("_mirror", fn)})
@@ -803,7 +803,7 @@ func (p *Package) buildGo(buildctx *buildContext, wd, result string) (err error)
 				return PkgNotBuiltErr{dep}
 			}
 
-			tgt := filepath.Join("_deps", dep.FilesystemSafeName())
+			tgt := filepath.Join("_deps", p.BuildLayoutLocation(dep))
 			commands = append(commands, [][]string{
 				{"mkdir", tgt},
 				{"tar", "xfz", builtpkg, "-C", tgt},
@@ -869,7 +869,7 @@ func (p *Package) buildDocker(buildctx *buildContext, wd, result string) (err er
 			return PkgNotBuiltErr{dep}
 		}
 
-		tgt := dep.FilesystemSafeName()
+		tgt := p.BuildLayoutLocation(dep)
 		commands = append(commands, [][]string{
 			{"mkdir", tgt},
 			{"tar", "xfz", fn, "-C", tgt},
@@ -941,7 +941,7 @@ func (p *Package) buildGeneric(buildctx *buildContext, wd, result string) (err e
 			return PkgNotBuiltErr{dep}
 		}
 
-		tgt := dep.FilesystemSafeName()
+		tgt := p.BuildLayoutLocation(dep)
 		commands = append(commands, [][]string{
 			{"mkdir", tgt},
 			{"tar", "xfz", fn, "-C", tgt},

pkg/leeway/package.go

@@ -111,14 +111,15 @@ func (n PackageNotFoundErr) Error() string {
 }
 
 type packageInternal struct {
-	Name                 string      `yaml:"name"`
-	Type                 PackageType `yaml:"type"`
-	Sources              []string    `yaml:"srcs"`
-	Dependencies         []string    `yaml:"deps"`
-	ArgumentDependencies []string    `yaml:"argdeps"`
-	Environment          []string    `yaml:"env"`
-	Ephemeral            bool        `yaml:"ephemeral"`
-	PreparationCommands  [][]string  `yaml:"prep"`
+	Name                 string            `yaml:"name"`
+	Type                 PackageType       `yaml:"type"`
+	Sources              []string          `yaml:"srcs"`
+	Dependencies         []string          `yaml:"deps"`
+	Layout               map[string]string `yaml:"layout"`
+	ArgumentDependencies []string          `yaml:"argdeps"`
+	Environment          []string          `yaml:"env"`
+	Ephemeral            bool              `yaml:"ephemeral"`
+	PreparationCommands  [][]string        `yaml:"prep"`
 }
 
 // Package is a single buildable artifact within a component
@@ -134,6 +135,7 @@ type Package struct {
 	Definition []byte `yaml:"-"`
 
 	dependencies     []*Package
+	layout           map[*Package]string
 	originalSources  []string
 	fullNameOverride string
 }
@@ -146,12 +148,19 @@ func (p *Package) link(idx map[string]*Package) error {
 	}
 
 	p.dependencies = make([]*Package, len(p.Dependencies))
+	p.layout = make(map[*Package]string)
 	for i, dep := range p.Dependencies {
-		var ok bool
-		p.dependencies[i], ok = idx[dep]
+		deppkg, ok := idx[dep]
 		if !ok {
 			return PackageNotFoundErr{dep}
 		}
+		p.dependencies[i] = deppkg
+
+		// if the user hasn't specified a layout, tie it down at this point
+		p.layout[deppkg], ok = p.Layout[dep]
+		if !ok {
+			p.layout[deppkg] = deppkg.FilesystemSafeName()
+		}
 	}
 	return nil
 }
@@ -239,6 +248,19 @@ func (p *Package) GetTransitiveDependencies() []*Package {
 	return res
 }
 
+// BuildLayoutLocation returns the filesystem path a dependency is expected at during the build.
+// This path will always be relative. If the provided package is not a depedency of this package,
+// we'll still return a valid path.
+func (p *Package) BuildLayoutLocation(dependency *Package) (loc string) {
+	var ok bool
+	loc, ok = p.layout[dependency]
+	if ok {
+		return loc
+	}
+
+	return p.FilesystemSafeName()
+}
+
 // UnmarshalYAML unmarshals the package definition
 func (p *Package) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	var tpe packageInternal

pkg/leeway/workspace.go

@@ -489,6 +489,18 @@ func loadComponent(ctx context.Context, workspace *Workspace, path string, args
 
 			pkg.Dependencies[idx] = comp.Name + dep
 		}
+		// make all layout entries full qualified
+		if pkg.Layout == nil {
+			pkg.Layout = make(map[string]string)
+		}
+		for dep, loc := range pkg.Layout {
+			if !strings.HasPrefix(dep, ":") {
+				continue
+			}
+
+			delete(pkg.Layout, dep)
+			pkg.Layout[comp.Name+dep] = loc
+		}
 
 		// apply variant config
 		if vnt := pkg.C.W.SelectedVariant; vnt != nil {

pkg/vet/docker.go

@@ -72,7 +72,7 @@ func checkDockerCopyFromPackage(pkg *leeway.Package) ([]Finding, error) {
 			// we've found something that looks like a path - check if we have a dependency that could satisfy it
 			var satisfied bool
 			for _, dep := range pkg.GetDependencies() {
-				if dep.FilesystemSafeName() == pth {
+				if pkg.BuildLayoutLocation(dep) == pth {
 					satisfied = true
 					break
 				}

pkg/vet/generic.go

@@ -32,7 +32,7 @@ func checkArgsReferingToPackage(pkg *leeway.Package) ([]Finding, error) {
 			// we've found something that looks like a path - check if we have a dependency that could satisfy it
 			var satisfied bool
 			for _, dep := range pkg.GetDependencies() {
-				if dep.FilesystemSafeName() == pth {
+				if pkg.BuildLayoutLocation(dep) == pth {
 					satisfied = true
 					break
 				}

pkg/vet/packages.go

@@ -0,0 +1,30 @@
+package vet
+
+import (
+	"fmt"
+
+	"github.com/typefox/leeway/pkg/leeway"
+)
+
+func init() {
+	register(PackageCheck("build-layout", "validates the build layout of all packages", "", checkBuildLayout))
+}
+
+func checkBuildLayout(pkg *leeway.Package) (findings []Finding, err error) {
+	layoutIdx := make(map[string]string)
+	for dep, loc := range pkg.Layout {
+		otherdep, taken := layoutIdx[loc]
+		if !taken {
+			layoutIdx[loc] = dep
+			continue
+		}
+
+		findings = append(findings, Finding{
+			Description: fmt.Sprintf("build-time location %v is used by %v and %v", loc, dep, otherdep),
+			Component:   pkg.C,
+			Error:       true,
+			Package:     pkg,
+		})
+	}
+	return
+}